An artificial foot of this kind is known from U.S. Pat. No. 5,913,902. The ankle joint is located in the axis of a tubular lower leg part of a below-knee prosthesis received by an adapter piece of the connecting part. The ankle joint and the joint between forefoot part and base foot part are pivotable independently of one another, the pivotability being elastically damped by compression springs fitted between the respective joint parts. This foot construction permits the use of the artificial foot with several heel heights, since the foot can be adapted to different angles of the forefoot and of the connecting part relative to the base foot part. However, the static arrangement in this case alters as a function of the heel height, so that widely different walking dynamics arise also as a function of the heel height.
DE 100 10 302 A1 discloses a prosthetic foot with a movable ankle joint and with a similarly movable forefoot part. The object of the disclosed foot construction is to substantially prevent dropping of the knee joint, and thus of the hip joint, during heel-to-toe movement across the toe area. To achieve this, a plantar flexion is sought between foot and lower limb, that is to say between base foot part and connecting part. For this purpose, a coupling rod is secured between the forefoot part and the base foot part, the securing in the base foot part being effected by an oblong hole. One end of the coupling rod protrudes into the area of the connecting part and, because of the bending of the forefoot part, limits the angle between connecting part and base foot part. By limiting the angle, further dropping of the knee, and thus of the hip, is avoided. Adaptation of the foot to different heel heights is neither provided for nor indeed possible in the described construction.
Prostheses are known in which the sagittal adaptation of the prosthetic foot can be done by the patient, in order to permit adaptation to different heel heights. A wrong adjustment cannot be ruled out. To ensure that the forefoot can adapt to the shape of the shoe, it is made soft. As a result, however, the load uptake in the forefoot area at the end of the stance phase is insufficient.